How to rotate tank treads animation using Bezier circle
If you parent the object to the curve, or if you parent both the object and the curve to an empty, it will work fine, as the axis will remain relative to the parent. If you don't, the object will go wild as you'll change the deform axis. Note that I also had to animate the tank treads on the right axis so that it moves along the curve, but it is the empty that makes it rotate.